if the track is bumpy you want a car with travel. The 2 cars that have the most travel is ae and mugen. Hara hb has the long rear shock set but still dont add the travel to compair with them. Same with the xray its a really nice car but shocks on american tracks just cant handle the big jumps and rought surfaces as easily. Now for the kyosho you spend the money for a great car and im sure it would be a great ride to run this on to but do you wanna club race a tki2?

I would say keep the mugen.

If you arent having any issues with the brand you run why change it? No buggy is just a drop it and race it and its easy to drive but what can help is running a 2wd buggy or even slash, they will teach you throttle control and handling. But the hot-bodies and jammin x1cr cars are the two cars that i have ran that seem to be really easy to handle and drive hard.

Next year I plan on going Serpent to try something different. I wasn't the biggest fan of the MBX6 when it came to the pillow ball (wished they just used normal hubs) but other then that the car was great. A ton of on power steering but not as much off power as the Losi with the setups I tried.

Long story short both great cars and I have seen the serpents do just as well. Can't go wrong with the choices you listed, should all be contenders.

thank for the comments.... just decided to go with the kyosho... I live in Costa Rica and we have a pretty competitive championship here... many people with mugen another bunch with losi 3 serpents that are really looking good for the time and more associated...